Aneroid barometers which use an evacuated chamber to detect changes in atmospheric pressure were developed as early as 1843. These devices are still very popular today and can be found in many homes. They also add aesthetic value because of their interesting design. Many consumers prefer the more traditional look of an analog barometer which uses a dial and a pointer to display current atmospheric conditions as opposed to the more modern digital devices which use an LCD type display [such as shown in the John Morley article “A Solid-State Barometer for the HCS II” in Home Automation & Building Control, October, 1995, pages 63-69; and the PIC based barometer instrument using a programmed PIC 16F876 Microcontroller described by Gary Sargent, Dec. 20, 2001, and available over the Internet at nutsvolts.com]. For the most part aneroid barometers work well enough for their intended purpose once properly calibrated but have several weaknesses which are hard to overcome.
First the construction of the aneroid chamber is very critical to the accuracy of the barometer and even when properly constructed over time the chamber may lose its ability to accurately respond to changes in air pressure as it was originally intended. This will cause the barometer to give incorrect readings and over time it may need to be re-calibrated. Also, in order to transmit the motion of the expansion and contraction of the aneroid chamber to the pointer a variety of mechanical linkages, levers and pivots need to be utilized. These mechanical linkages may cause further error to be introduced if they are not of the highest quality. This is why many consumers are turning their interest toward the newer, more accurate, digital barometers.
In the last few decades there have been many advances in electronic technology which have made it possible to produce very accurate digital barometers with LCD type displays. These barometers are now much more affordable due to the large volume of product being produced.
According to one aspect of the invention, a barometer is provided which combines the best of existing analog and digital barometers. The invention provides an analog dial type barometer which will retain the look and feel of a traditional barometer but have the accuracy and resolution of a modern digital barometer. This digital to analog barometer incorporates many features which makes it unique relative to anything that is currently available. While digital to analog pressure gauges are known per se [e.g. see U.S. Pat. No. 6,394,977, hereby incorporated by reference herein] they have not been used for a barometer, let alone with many of the advantageous features according to the invention.
An electronic barometer movement used in the invention is easy to use, install and calibrate. The movement will be more accurate than any aneroid movement currently available and will provide a level of resolution of plus or minus one millibar of pressure or less [e.g. about 0.5 millibar].
Using a movement according to the invention, instead of an existing conventional aneroid barometer movement, an existing manufacturer of clocks could easily be in production of an entirely new line of products within days of deciding to do so. The barometer movement of the invention can be installed into any existing clock housing as quickly as any quartz clock movement. The digital barometer movement is also far more robust and less difficult to handle than a typical aneroid movement. The only change that a manufacturer need make aside from using the barometer movement will be to change the artwork from that of a clock dial to that of a barometer dial.
An exemplary barometer according to the invention will fit into the same space as a quartz clock movement, that is approximately 2⅛ by 2⅛ by ⅝ inches [5.4 cm by 5.4 cm by 1.6 cm]. One of the primary advantages will be the ability of this movement to mount to a dial or housing using a threaded bushing and to also utilize a much larger hand or pointer than any conventional barometer. Most aneroid movements can only turn a hand that is balanced and even so there is a restriction on the weight of the hand due to the delicate mechanical nature of aneroid movement design. A typical aneroid barometer movement is usually not used to produce barometers with dial diameters of greater than eight inches [20 cm]. The average is between four and six inches [10 and 15 cm] for most barometers in use today therefore the typical pointer which an aneroid barometer may use is usually not more than three inches [7.5 cm] from center to tip. In addition if the pointer is not balanced the barometer will not function properly. This presents a problem if there is a desire to produce a barometer with a large diameter dial, for example about ten to twenty inches [25-51 cm] in diameter. There is no known prior art solution to this problem.
One of the problems associated with a large pointer is the increased weight of the pointer. A typical aneroid barometer can only tolerate a pointer that weighs a fraction of a gram. Some conventional aneroid barometer pointers weigh as little as 0.1 of a gram to about 0.25 of a gram. However, according to the electronic barometer of the invention a d.c. motor is used to drive the analog pointer, and the motor is geared so that the barometer will be capable of swinging a much larger pointer than any conventional aneroid barometer. A pointer weighing up to about 5 grams [e.g. about 3 to 5 grams], or even more, can be used; and the pointer does not have to be balanced though providing a balanced pointer will allow the use of an even larger pointer. The movement can use a pointer of up to ten inches [25 cm] from center to tip if balanced allowing the construction of a barometer which can exceed twenty four inches [61 cm] in diameter. A more typical pointer size is about six inches [15 cm] in length from center to tip and this size of pointer will not have to be balanced. By using this size pointer a manufacturer will be able to produce a barometer of sixteen inches [41 cm] in diameter, far greater than anything currently available on the market today.
One of primary features of the barometer movement according to the invention is its ability to use as a pointer any one of the thousands of readily available clock minute hands from hundreds of suppliers around the world. Current analog barometers are limited to the type of pointer they can use and are usually supplied by the barometer manufacturer. The biggest advantage of using a standard non-balanced clock hand as a pointer is that it allows the manufacturer the flexibility to select a style of pointer that suits its particular design. It is simple to match a new barometer to an existing clock that may already be part of an existing product line. The electronic barometer of the invention preferably has an output shaft which will allow any existing pointers, including conventional clock hands, to be conveniently used.
The invention also has a broader aspect than use in a pressure change indicator in general, or barometer in particular. The invention can also be used in association with temperature (alone) and/or humidity transducers. There are many known temperature transducers (which convert sensor readings into some sort of electrical signal), as well as humidity transducers. Some examples of temperature transducers are in U.S. Pat. Nos. 5,201,840, 5,820,262, and 6,654,894, and some examples of humidity transducers are in U.S. Pat. Nos. 5,608,374, 5,652,382, and 6,073,480.
Atmospheric pressure (or temperature or humidity) does not usually change very rapidly so to preserve battery life and still maintain accurate readings, the barometer/indicator of the invention will utilize a “sleep” or “idle” mode/feature. The software which controls the micro processor will put the device to “sleep”. By running the microprocessor in sleep or idle mode, the device will only check the status of the pressure transducer once every minute, five minutes, or any other time interval deemed appropriate, and as desired by the parameters set in the software. The longer the sleep time interval the longer the battery will last. It is estimated that a sleep time interval of one minute will allow an exemplary 3.6 volt lithium battery to last two years or more, and a sleep interval time of five minutes will allow the battery to last for over five years [with similarly proportional times for other types of batteries]. If this feature is turned off or not used the battery will only last about five to ten days.
The instrument (e.g. barometer) movement according to the invention preferably uses a battery or batteries providing about 2.5-5 volts. A single 3.6 volt lithium battery is preferred, however two standard 1.5 volt alkaline batteries, or other conventional or to be hereafter developed, batteries can be used.
The movement preferably also has a low battery warning provision built into the software. The software will be able to be set to check the status of the battery voltage. When the voltage drops below the value set in the software the microprocessor will send an audible signal to a piezoelectric horn [or other audible, visual—such as a flashing light or LED—and/or tactile alarm] alerting the user that the battery needs to be changed. In one embodiment, for the 3.6 volt lithium battery, a voltage of 2.5 will cause the alarm to be activated.
The instrument (e.g. barometer) of the invention also has the ability to detect a significant change in environmental conditions (e.g. drop in barometric pressure) and to initiate a warning, e.g. using the piezoelectric horn, flashing light or LED, or other alarm. This alerts the user to an impending environmental condition change (e.g. bad weather). Typically the alarm type, period, or other characteristics will be varied to distinguish the low battery alarm from the bad weather alarm. For example the low battery alarm may be provided by short, intermittent, activations of the horn, while the bad weather alarm will be full scale continuous operation of the horn.
The microprocessor in the movement of the invention has the ability to store multiple pressure (and/or other environmental condition) readings over any period of time in memory. This information can be used to determine very specific rate of change of pressure data and can be used to detect adverse changes in weather. For example if the pressure drops by one millibar every five minutes for one hour the software can detect this and sound the alarm. The parameters can be set to any specified pressure drop over any duration of time and are from higher to lower pressures. The microprocessor will then send a signal to the piezoelectric horn or other alarm when that specified parameter is met. Alternatively, a second dial, pointer, and motor may be utilized to provide an analog indication of whether barometric pressure is steady, increasing, or decreasing, and by what rate.
Another desirable feature of the invention is the ability to configure the software to adjust the scale the barometer uses to display a particular pressure. The software can be adjusted to allow for wide variety of different scales. For example a standard barometer displays four inches of mercury on a 360 degree linear scale. However, it is sometimes desirable to display only two or maybe three inches [5-7.6 cm] of mercury on the same 360 degree linear scale. This gives the user much more activity of the needle/pointer and result in a high sensitivity barometer. In the case of a standard aneroid barometer it is impossible to change the scale unless the barometer is designed that way at the factory. In some parts of the world the changes in pressure are very small but they do occur, this is a particular situation when this use of a high sensitivity scale will be useful. The scale may even be adjusted [depending upon the pressure transducer utilized] so that the barometer functions as an altimeter. Of course the scale will also be adjusted if the indicator is used to display temperature or humidity in an analog manner.
The movement of the invention may have a simple push button switch [or other actuator] on the back of the housing to allow the user to set the pressure to the current conditions. The switch will interrupt the sleep mode when activated and allow the unit to be adjusted at any time.
According to one aspect of the invention there is provided a digital to analog barometer comprising: A dial with barometric indicia. A pointer operatively connected to a shaft for movement with respect to the dial. A pressure transducer positioned to sense barometric pressure and convert the pressure sensed to an electrical signal. A d.c. motor operatively connected to the pointer shaft. A microprocessor; and a battery. The pressure transducer, d.c. motor, and battery are operatively connected to the microprocessor so that the microprocessor accurately controls movement of the motor with power supplied by the battery in response to changes in pressure sensed by the pressure transducer, the motor in turn changing the position of the pointer with respect to the barometric indicia on the dial.
That is, according to one aspect of the invention there is provided a barometer comprising: a pointer operatively connected to a shaft for movement with respect to a dial; a pressure transducer; a d.c. motor [preferably a stepper motor] operatively connected to the pointer shaft; a microprocessor; and a battery; the pressure transducer, d.c. motor, and battery operatively connected to the microprocessor so that the microprocessor controls movement of the motor with power supplied by the battery in response to changes in barometric pressure sensed by the pressure transducer, characterized by: the pressure transducer is capable of sensing barometric pressure and positioned to sense barometric pressure; and a dial having barometric pressure indicia thereon positioned adjacent the pointer so that the pointer sweeps over the dial; the motor accurately changing the position of the pointer with respect to the barometric indicia on the dial under the control of the microprocessor in response to changes in barometric pressure sensed by the pressure transducer.
The d.c. motor most desirably comprises a conventional stepper motor, such as one having an hour shaft used in a conventional quartz clock movement, with the pointer shaft operatively connected to the hour shaft. However other d.c. motors which have positional feedback and can rotate the shaft either clockwise or counterclockwise (anti-clockwise) may sometimes be utilized, including servo motors with feedback circuitry, and piezoelectric motors with feedback [such as shown in U.S. Pat. No. 6,867,532]. The dial may have a diameter of at least about 10 inches [25 cm], and the pointer may have a radius of at least about 5 inches [12.5 cm], and the pointer may be balanced or unbalanced, and have a weight of at least 0.3 or 0.4 grams, e.g. at least about 2 grams.
The pressure transducer, battery, microprocessor, and stepper motor may be mounted in a housing operatively connected to the back of the dial. The dimensions of the housing may be approximately 2⅛ [5.4 cm] by 2⅛ [5.4 cm] by ⅝ [1.6 cm] inches, with the pointer shaft extending outwardly from the housing. A temperature sensor is preferably also mounted in the housing, and operatively connected to the microprocessor so that pressure determinations from the pressure transducer are temperature compensated. Still further, the housing may contain a battery voltage sensing circuit, and an alarm operatively connected to the microprocessor and activated by the microprocessor when the battery voltage as sensed by the battery voltage sensing circuit drops to or below a predetermined threshold. The alarm may also be activated, in a different mode than when the battery voltage drops, or a second alarm may be activated, if the pressure change between two or more substantially consecutive pressure readings [e.g. spaced more than about one minute apart] is greater than a predetermined threshold. Preferably the microprocessor controls the battery so that the battery is substantially in an inactive mode more than 90% (e.g. more than 95%) of the time. The battery may comprise a single about 3.6 volt lithium battery, or two or more about 1.5 volt alkaline batteries
The barometer may further comprise a second dial, and a second pointer having a second shaft operatively connected to a second d.c. motor with positional feedback, and the second motor connected to the battery, so that the microprocessor records pressure transducer readings over an extended period of time and controls the second d.c. motor to position the second pointer with respect to the second shaft to indicate atmospheric pressure trends.
According to another aspect of the present invention there is provided an indicator comprising: A dial with indicia thereon. A pointer operatively connected to a shaft for movement with respect to the dial. A pressure, temperature, or humidity transducer positioned to sense pressure, temperature, or humidity. A d.c. motor with positional feedback operatively connected to the pointer shaft. A microprocessor; and a battery. The transducer, d.c. motor, and battery are operatively connected to the microprocessor so that the microprocessor controls movement of the motor with power supplied by the battery in response changes in pressure, temperature, or humidity sensed by the transducer, the motor in turn accurately changing the position of the pointer with respect to the indicia on the dial; and the transducer, battery, microprocessor, and d.c. motor are mounted in a housing operatively connected to the back of the dial, the housing having dimensions of approximately 2⅛ [5.4 cm] by 2⅛ [5.4 cm] by ⅝ [1.6 cm] inches, with the pointer shaft extending outwardly from the housing past the dial. The dial and pointer may have the dimensions and weights as set forth above. The indicator may further comprise an alarm, and battery voltage sensing circuitry, mounted within the housing and operatively connected to the microprocessor and activated by the microprocessor when the battery voltage, as sensed by the circuitry, drops to or below a predetermined threshold; and the microprocessor may control the battery so that the battery is substantially in an inactive mode more than 90% of the time. Where a pressure transducer is used, temperature compensation for the pressure transducer may also be provided, as described above.
According to another aspect of the invention there is provided a barometer, temperature, or humidity movement per se comprising: A plurality of elements including a pressure, temperature, or humidity transducer capable of sensing barometric pressure, temperature, or humidity and converting the sensed condition into electric signals; a stepper motor having an hour or minute shaft used in a conventional quartz clock movement; a microprocessor; and a battery, the elements operatively connected together so that the microprocessor controls movement of the stepper motor with power supplied by the battery in response changes in an environmental condition (e.g. barometric pressure) sensed by the transducer. And a housing mounting the plurality of elements with the motor shaft extending outwardly from the housing.
That is, according to this aspect there is provided an instrument movement comprising: a transducer capable of sensing barometric pressure, temperature, or humidity, a microprocessor, and a battery mounted in a housing, characterized by a stepper motor having an hour or minute shaft used in a conventional quartz clock movement with the motor shaft extending outwardly from the housing; the battery, stepper motor, transducer, and microprocessor being operatively connected together so that the microprocessor controls movement of the stepper motor with power supplied by the battery in response changes in atmospheric pressure, temperature, or humidity sensed by the transducer.
The movement may further comprise an alarm, and battery voltage sensing circuitry, mounted within the housing and operatively connected to the microprocessor and activated by the microprocessor when the battery voltage, as sensed by the circuitry, drops to or below a predetermined threshold. Preferably, the microprocessor functions so that the alarm is also activated, in a different mode than when the battery voltage drops, or a second alarm is activated, if the condition sensed [e.g. barometric pressure] change between two or more spaced readings [e.g. spaced more than about one minute apart] is greater than a predetermined threshold. Where a pressure transducer is provided, the housing also preferably includes a temperature sensor mounted within the housing and operatively connected to the microprocessor so that pressure determinations from the pressure transducer are temperature compensated. Preferably the microprocessor controls the battery so that the battery is substantially in an inactive mode more than 90% (e.g. more than 95%) of the time.
It is the primary object of the invention to provide a digital to analog indicator and movement that are versatile, relatively inexpensive, accurate, and simple to construct, and are particularly useful for displaying barometric pressure, but also useful for displaying other pressure values, temperature, and/or humidity. This and other object of the invention will become clear from the detailed description of the invention, and from the appended claims.